In recent years, advancements in electronic imaging technology have been remarkable. More specifically, more compact electronic still cameras with higher picture quality have been realized. Additionally, with the recent arrival of the electronic information age, the likelihood of electronic still cameras becoming widely used is excellent.
However, electronic still cameras are still expensive for their performance as compared with conventional photographic cameras that use silver chloride film, and this has been an obstacle to the wider popularity of electronic still cameras. Thus, there is strong need for a low cost, wide-angle zoom lens that is particularly suitable for use in electronic still cameras.
However, there have been many wide-angle zoom lenses designed heretofore. For example, Japanese Laid-Open Patent Application HO7-113956 discloses a two group, wide-angle zoom lens having, in order from the object side, a negative first lens group and a positive second lens group. This wide-angle zoom lens requires at least seven lens elements. Also, a comparatively wide-angle, four-group zoom lens is disclosed in Japanese Laid-Open Patent Application HO9-179026. This zoom lens is composed of, in order from the object side, a negative first lens group, a positive second lens group, a negative third lens group and a positive fourth lens group. This zoom lens also has at least seven lens element. It would be inaccurate to describe these conventional wide-angle zoom lenses as compact and inexpensive. Thus, development of a high performance, compact and inexpensive, wide-angle zoom lens specifically suited to an electronic still camera is desire.
Japanese Laid-Open Patent Application HO6-201993 descloses a two focal point lens that has a wide-angle position. This lens includes at least eight lens elements, with a diameter of the front lens group being comparatively large. Thus, the disclosed lens therein does not satisfy the need for a compact and inexpensive, wide-angle zoom lens suitable for use in an electronic still camera.
As is evident from these conventional examples, in order to obtain a compact zoom lens having high performance that is composed of only a few lens elements, a wide-angle zoom lens with a short focal length relative to the image size is desired. However, there is the problem in that, as the outer diameter of the lens increases in size at the wide-angle end where the image angle of the zoom lens increases, the lens barrel diameter must also increase and compactness is lost.